1. Field of the Invention
The present invention relates to a position detecting apparatus, and more particularly, to a position detecting apparatus for a movable optical member such as a zoom lens, a focus lens, or an iris of a lens apparatus, or a position detecting apparatus for a movable optical member within a scanning optical apparatus such as an image reading apparatus or an image forming apparatus, and to a lens apparatus, an image reading apparatus, and an image forming apparatus that include the position detecting apparatus.
2. Description of the Related Art
At present, controllability of very high-precision is required for robot control, lens control for a camera, and the like. In order to realize this controllability, a high-precision and small position detecting apparatus is required.
In Japanese Patent Application Laid-Open No. 2012-220458, there is proposed a position detecting apparatus configured to use patterns having a plurality of different spatial modulation periods and a detection element array arranged in a movement detection direction to obtain the phase of each of a plurality of modulation signals, to thereby calculate the position. The use of this position detecting apparatus enables high-precision position detection.
In the related art disclosed in Japanese Patent Application Laid-Open No. 2012-220458, signals output from the detection element array are separated from a plurality of different modulation signals into specific modulation signals by using the principles of a spatial filter. However, with the spatial filter, the perfect separation cannot be carried out. Thus, when a desired modulation signal is intended to be obtained, other modulation signal components remain to distort a signal waveform. As a result, position detection precision is reduced.